Monday, August 30, 2010

Trees have stretch marks too!

Have you ever noticed the stretch marks on trees?

Trees grow in height as well as in diameter. Some trees, like the sycamore, allow for the increase in trunk diameter by shedding bark, an all too common occurrence in the spring in my neighborhood.  

Ash, elm and many other trees develop cracks in the bark that run up the trunk.  As new wood and bark is produced under the older outer bark, these cracks allow the tree to expand. 

Cracks also form in the bark when the trunk bends as you can see in the next photo.   

These cracks are normal.

Sunday, August 29, 2010

Some Trees are not worth Saving!

This aspen has a canker disease eating away at its trunk.  The disease invaded the tree through a branch stub at least five years ago as can be seen by the annual growth pattern of the damage. 

The fungus feeds during the winter when the tree is at its weakest.  With the onset of Spring, the tree's vigor improves as leaves emerge and photosynthesis begins.  When sugars reach the injured site new callus tissue forms and stops the spread of the fungus. This callus tissue is invaded and killed as soon as the fungus regains control of the tree.  This cycle happens again and again until the tree no longer has the tissue necessary to keep the tree together.  At some point this tree will break at the canker. 

The fungus that causes this problem, known as Black, Target and Ceratocystis canker, is Ceratocystis fimbriata.

Applying nitrogen around the tree after the leaves emerge in the spring will increase tree health.  Two pounds of nitrogen per 1000 square foot area surrounding the tree is the recommended amount to use.  Unless you have had a soil test conducted that shows phosphorus and/or potassium levels are deficient, these nutrients should NOT be applied.  Ammonium sulfate is a good synthetic nitrogen source to use.  Blood meal, cotton seed meal, corn gluten and other organic products are also good nitrogen fertilizers.

Note:  The cat scratches on the trunks are cause for concern. There is a good chance this fungus will be spread to the other trees by the claws of the cat. Removing the infected trunk will help prevent the spread of the fungus.

Wednesday, August 25, 2010

Poplar twiggall fly causes serious damage.

The poplar twiggall fly is often said to cause little damage to the aspen this insect attacks.

Dead Shoot as a reult of this insect

The vascular damage this insect causes can result in the death of twigs as seen in the photo to the left. 

If these galls are in the main stem of the tree, can the area damged by this insect break off?

An application of imidiclopyrid once a year will take care of this problem.
Note Exit Holes

Tuesday, August 24, 2010

cucumber sun burn, watermelon sunscald

Charleston Gray and other melons can suffer from sunburn
Watermelon, cucumbers and many other vegetables can be burned by the sun.  This causes white spots on the skin  that extends into the flesh.  This dead flesh may be attacked by saprophytic fungi such as Botrytis and Aspergillus.

While the black spots and smugs caused by fungus are often thought to be the cause of the problem, the intense rays of the sun not providing shade is the problem.

Cucumber with sunburn and a fungus infection.

Covering the fruit with the vines, straw or hay can help prevent this problem.

Monday, August 23, 2010

Maple anthracnose may be due to spring weather.

Anthracnose is the term used to describe a disease that causes limited, sunken dead spots such as those on these maple leaves.  The disease organisms involved vary with the plant but they all require the same environmental conditions, wet and cool spring weather.

This year's spring was ideal for these diseases.  Control is an option that requires frequent sprays from bud break until the weather conditions change.  As soon as warm weather arrives the infection cycle of the disease organism is shut down.

At this time of year there is no reason to spray.  Cleaning up the leaves in the fall may reduce a source of this disease for next year's infection cycle.  

The sprays and spray schedule recommended for Sycamore anthracnose should be followed if you want to prevent anthracnose.  If next spring is warm and dry, there is no reason to spray.

Friday, August 20, 2010

Armenian cucumbers may split open if left on the vine too long.

Jude Sirota provide me a number of cucurbit plants (members of the gourd family) for the Grand Junction Community Garden at the Library earlier this year. One was an Armenian cucumber. This striped Armenian variety is called "Painted Serpent".

You can tell by the one Susan Swift is holding they can become quite long and certainly do resemble a serpent.

If you aren't familiar with this cucumber, they stay tender no matter how long they grow.

The only problem I've had with this cultivar is they split along the stem end. The damage shows up as open sores which enlarge into large splits as seen below.

This problem may be due to too much soil moisture.  Slicing cucumbers tend to become bitter when they lack adequate soil moisture.  Which is worse, a cucumber that is bitter or one that splits open?

Thursday, August 19, 2010

Glyphosate damage on ash tree.

This photo of an ash tree shows symptoms of glyphosate uptake. Glyphosate, initially sold as Roundup by Monsanto, is now available in generic form at many farm cooperatives, and retail businesses.  When this product is misapplied it can cause damage.  In this case the owner sprayed glyphosate to control weeds at the base of the tree last year.   These symptoms appeared this year.

Glyphosate may drift onto the buds or be taken in through green tissue at the base of tree . 

Symptoms of glyphosate toxicity the year after glyphosate uptake results in clusters of leaves where shoots should develop.  I've seen these same symptoms on trees in local retail nurseries where the wholesale nursery applied glyphosate to control weeds around the trees the previous year. These symptoms are also occasionally seen on grape vines when glyphosate is used to control weeds at the base of the vines.

Herbicides should be used with care.  Don't assume they are safe.

Monday, August 16, 2010

Pumpkin and squash mildew kills plants.

Powdery mildew, a common problem of roses, turfgrass and many other plants, also is a problem for squash and pumpkin especially when we experience the cool, humid conditions of fall.

This fungal disease destroys the photosynthetic ability of the leaves reducing the quality, size and yield of the fruit. 

The first syptoms you will see are white spots on the leaves.  These spots increase and eventually cover the leaf. This disease reduces the sugars and starches necessary for the development and sizing of the fruit.

Controlling this disease is quite easy if you use the correct product or combination of materials.  Some people use SunLite oil in combination with baking soda as a spray.  A better product to use is potassium bicarbonate.  Baking soda can damage plant cells; potassium bicarbonate is much softer in its activity.  Neem oil is also reported to be an effective control of powdery mildew.  Your local nursery or garden center should have one of these products on their shelves.

These products are best applied in the evening as they remain in the liquid state for a longer period of time.  If a rain occurs shortly after you make the application you will most likely need to reapply the product.  You will still see spots on the leaves even after you treat for this disease, but as long as the spots don't enlarge or more spots don't develop, the infection has been stopped.  Follow the label to ensure you apply these at the proper dilution and frequency.

Sunday, August 15, 2010

When should you harvest pumpkins and winter squash?

I  recently harvested two pumpkins. Neither was completely orange but I could not puncture the skin with a finger nail, the stage at which they are ready to harvest. Instead of leaving these pumpkins I cut them off the vine and put them on my back stoop. They continued to ripen and are now uniformly orange.

If you leave pumpkins and winter squash on the vine even though they are ready to harvest, you run the risk of them being damaged by insects or vandals.

Harvest your pumpkins and winter squash as soon as they are ready. If you can cut their rind with a finger nail they are not ready to harvest; when the rind can no longer be cut with a finger nail they need to be harvested.

Always leave a portion of the stem attached to the fruit.  Otherwise you run the risk of a disease organism invading the fruit causing rot.

Friday, August 13, 2010

Do tomatoes experience live birth?

Unless you look closely, it looks like maggots are growing under the skin of this tomato. In this photo I removed the skin of the tomato to give you a closer look. Who would want to eat a tomato riddled with maggots?

Some of these ‘maggots’ have even pushed through the skin and are invading the air space surrounding this tomato. In the photo immediately below you can see other 'maggots' that have escaped through the skin and others that are about to escape.

These ‘maggots'’ turn out to be tiny tomato plants. The seeds germinated inside the fruit and the baby seedlings pushed their way to and even through the skin of the tomato. This is called vivipary.

Why did the seeds germinate and begin to grow? Seed dormancy is usually terminated by low temperatures or by the application of a plant growth substance such as ethephon.

Ethephon is often applied to tomatoes to enhance ripening or to ensure all the tomatoes in an order are the same shade of red when they arrive at the grocer. Was this tomato treated with ethephon or was another substance applied? Or did something else trigger the germination of the seeds?

Wednesday, August 11, 2010

Corn Smut is quite a delicacy!

Sweet corn is a tremendous treat.  I especially like the Sugary Enhanced (SE) varieties created by Dave Gallinat of Mesa Maize in Olathe, Colorado. Many of his hybrids are sold as 'Olathe Sweet' sweet corn throughout the United States.  I even took some of his seed to Armenia when I worked over there in 1994.  The Armenians were definitely impressed with the sweet ears his seed produced.

Sometimes you get a bonus when corn smut develops along with the ear.  The smut balls growing out of the ear of corn Susan Rose, Horticulture Educator for our four-county area, is about to take a bite out of arrived in our office this afternoon. As far as I'm concerned this smut has already gone beyond what I would consider the edible stage.  Others disagree as they like the more mature smut flavor.

Four to five hundred tons of this fungus are sold in Mexico City every year.  In the United States, increased interest in this fungus is due to an increase in the Mexican-American community and the rising interest in new foods. Chefs in high-end restaurants are reported to pay $30 to $40 for 2 pounds of this mushroom.

Caused by the fungus Ustilago maydis, corn smut, is called huitlacoche by those in the know.  Like puffballs, the gleba, the inner spore bearing mass, is initaily nice and white, turning into black spores as seen  with the smut ball on the left side of this photo.  That smut ball has broken open releasing black spores.

Even small backyard producers may find the production of huitlacoche profitable.  If you are interested, check out Purdue University's article on how to  produce this unusual agricultural product. 

Hackberry leaf spots may be insect caused.

Hackberry (Celtis spp.) leaves often have spots on the upper surface that looks somewhat like measles or blisters but are light green or yellow in color.

These spots are caused by the Hackberry Blistergall maker (Pachypsylla celtidisvesicula). The blisters are 3 to 4 mm in diameter and only slightly raised from the leaf surface.

There are 25 millimeters (mm) in an inch so these spots are quite small.

When you flip the leaf over you will see and can feel many tiny bumps. The feeding activity of this psyllid stimulates the tissue into forming a gall, an abnormal growth.

[Pysyllids are  known as jumping plant lice due to their tendency to jump when disturbed.]

You may find blistergall makers and nipplegall makers on the same leaf as is seen in the next photograph.  The nipple-like galls are due to the feeding activity of Pachypsylla celidismamma.

 Note the three nipple galls mixed in with the galls of  the hackberry blistergall maker.

Psyllids feed by inserting their mouth parts into the phloem of the tissue and sucking out the plant's juices.  They tend to feed on either a single type of plant such as the hackberry or members of the same family of plants.  Consequently you do not have to worry about these insects feeding on any plants other than hackberries.

There is one generation of these gall makers per year with the eggs being laid as the leaves unfurl in the spring.  A dormant or horticultural oil applied to the tree to coat the overwintering adults helps control this insect.  The use of a product containing the insecticide imidacloprid this fall will solve next spring's hackberry psyllid problems.

While this insect is more cosmetic than damaging, one can easily see why homeowners are concerned when they have an infestation of these leaf-disfiguring insects on their hackberry trees.

To learn more about psyllids check out the Psyllid web site.

Tuesday, August 10, 2010

Do you know when your sweet corn is ready to harvest?

Sweet Corn typically takes 21 days from the time each ear forms silk until it is ready to harvest. Each corn plant will form several ears over several days to a week. This may mean you will be harvesting over several days or all at once depending on the weather and heat units.

As harvest day approaches the silk will turn brown and dry out. You also should be able to feel the plump kernels through the husk. To make sure it is ready, strip down part of the husk and pierce a kernel with your finger nail. If white juice squirts out, the ear is ready to harvest. If the juice is clear, roll the husk back up and check it again in a day or two.

Once the corn is ready to harvest, don't wait. It is amazing how many gardeners decide to leave their corn until the next morning only to find the raccoons harvested their corn that very night.

Sunday, August 8, 2010

How do you know when to harvest Tomatillo?

The tomatillo or husk-tomato produces a great fruit wrapped in a husk. In the case of the larger-fruited types, when the husk is still green and the fruit has not filled the husk, the fruit is not yet ready to harvest.

If you grow the large-fruited type of tomatillo, they are best harvested when the husk has changed color, and the fruit has broken through and turned yellow-green. I have been told tomatillo are best used before the seeds are well developed.

If you have better suggestions on how to determine when to harvest this fruit leave a comment.

What an Ugly Tomato!

We all know tomato fruit splits due to uneven soil moisture (i.e. wet and dry period) and/or the inability of the plant to take up enough moisture during fruit development.

When moisture uptake is limited, tomato fruit stops enlarging and the skin of the fruit goes from the consistency of flexible rubber to the consistency of a brittle plastic. When the plant again moves water to the fruit, the fruit begins to enlarge and the skin cracks.

The cracks on some varieties of tomatoes will form concentric circles around the stem while other varieties will crack from the stem end toward the blossom end. To prevent this from happening we need to keep the soil uniformly moist and improve conditions that will allow the roots to move water to the leaves and fruit.

When some tomatoes crack and again start to grow, they grow out of the crack producng strange looking fruit. Split fruit are also highly susceptible to various rots.

Tuesday, August 3, 2010

Conks mean Trouble for Trees and People!!

A conk is the fruiting body of a fungus that infects trees. Trees exhibiting conks, bracket fungi, or mushrooms on the bark are hazardous to your health as well as the health of the tree.

By the time a fruiting body is visible, decay is extensive throughout the interior of the tree. The conk on this juniper is most likely Juniper Pocket Rot (Pyrofomes demidoffii).

According to Gail Durham, Forest Health Specialist. Nevada Dept of Forestry, "this white rot fungus creates "small pockets filled with white to yellowish cottony fibers of decay .. the tree’s foliage declines, thins out and only small tufts are seen near the end of the branches."

These pockets of light-colored spongy masses are separated by thin areas of firm wood. As more pockets of woody tissue become infected and decay, less and less firm wood is present to keep the tree from failing. These decayed spongy areas can extend 13 feet or more in either direction from the fruiting body of the fungus making infected trees a serious hazard to people and property. There is no telling when infected trees will fail and fall.

Some of the junipers in this neighborhood park have small tufts of needles near the end of the branches. No conks are visible on the trunk but the trees certainly exhibit the symptoms described by Ms. Durham.

White rot fungi invades trees through wounds such as those caused by humans and insects. The next photo shows the exit holes of one of the borers.

What can you do about trees infected with this or any other white rot fungus? Not a thing other than remove them before they break off and kill someone. Such trees are hazardous to your health.
Be sure to stay a safe distance away from any tree that has conks, mushrooms or bracket fungi on it trunk. Teach your children to recognize these strange growths so they will know not to play around white rot infected trees.

Monday, August 2, 2010

Fruit tree pests still need to be controlled

In today’s fruit tree update by Dr. Ramesh Pokharel, Western Colorado Research Center the following treatments are recommended.

“Codling moth (CM): We are still catching substantial numbers of second generation moth in our traps. It suggests us that we need protection against this pest beyond August 1. You also may need an additional spray beyond August 1 depending upon the activity of moths, the protection window of your insecticide used and harvesting date.

Peach Twig Borer (PTB): We are catching higher numbers (more than previous weeks) of second generation PTB month in our traps. This suggests a need to protect crop against this generation. Control of this generation is important as this generation can feed on fruits.

Crown Borer: The Crown borers are active in our orchard. Please, remember to have two sprays (a cover and a follow-up spray) to protect your crop from this pest. If this borer is active even after second spray, we might need a third spray during fall (trunk spray). Keep eye on this pest.”

To ensure good quality fruit and the survival of your fruit trees, treatments for these pests need to be applied and/or continued. Information on these pests and their control is available at and .

If you have specific questions call my office at 970 244-1836.